Installed 10.11 on my 4,1 (Early 2009) Mac Pro. Said install required putting the old video card back in and do a PRAM reset before the installation would complete, but, all appears fine now, except the monitor connected via DisplayPort isn't getting a signal and isn't showing up as I'd expect it to in the System Preferences area. I'm hoping to get back up and running with both displays (they were working in Yosemite). 10.11 Installation Steps: Remove GTX 760, install original GT 120 Reset PRAM Boot into recovery mode Partition / erase boot drive Install 10.11 Restore profile from Yosemite with Migration Assistant from Time Machine backup Remove GT 120, install GTX 760 Pertinent System Details: MacPro (4,1) Original video card (GT 120) removed PNY NVIDIA GeForce GTX 760 2048 MB (not flashed, aftermarket GPU fan/heatsink) DVI -> Generic Dell display (working) DisplayPort -> Dell HiDPI display (not working) Troubleshooting thus far: Have double checked all connections between computer and monitor Monitor is getting power, turned on, and set to correct input Installed web driver, no luck there with it native or web driver enabled after reboots This problem happened sporadically with Yosemite, but DisplayPort would come back after a reboot or two No difference after a sudo nvram boot-args=nvda_drv=1 nv_spanmodepolicy=1 The profile I'm using now started life in a Hackintosh with 10.6.2 many moons ago... not sure if it's possible there are any KEXT files that can sneak through with Migration Assistant that could be causing this, but, figured it's worth mentioning. Also worth mentioning: I installed an aftermarket GPU cooler to keep the noise level down. That required removing the existing heatsink and adding a new one, which required handling the card a fair amount. I've done enough DIY upgrades before I'm confident I didn't screw it up too badly, but, physical damage from the user isn't outside of the realm of possibility. Thoughts, any? Thanks in advance.